This invention relates in general to couplings between movable mechanical members and in particular to an improved coupling structure for connecting a movable link member of an actuator assembly to a movable valve spool in a fluid control valve.
In many hydraulic and pneumatic systems, control valves are provided for controlling the flow of fluid (either in liquid or gaseous form) from a pressurized source to one or more controlled devices. Most fluid control valves of this type include a case having a bore formed therethrough. Within the bore, a valve spool is mounted for limited axial movement. The valve spool has a plurality of circumferential grooves formed thereabout. A plurality of ports are formed in the case which communicate with the bore by means of respective passageways. The various ports of the control valve communicate with the pressurized source, the controlled devices, and a fluid reservoir. By moving the valve spool axially within the bore, certain ports are placed in fluid communication with other ports. As a result, the operation of the controlled devices is regulated in a desired manner.
A variety of structures are known for effecting movement of the valve spool relative to the case. In many fluid control valves, a manually operable handle is pivotably mounted on the case. The handle is typically connected through a link member to the valve spool such that manual pivoting movement of the handle causes axial movement of the valve spool. Manually operable fluid control valves such as this are suitable for use in hydraulic and pneumatic systems where it is possible to locate such fluid control valves conveniently for an operator to grasp and manipulate.
In other hydraulic and pneumatic systems, the fluid control valves are not or cannot be so conveniently located. In those systems, the fluid control valve is provided with a remotely controllable actuator in lieu of the manually operable handle. The actuator includes an internal member which is movable in response to an external signal generated by the operator. Movement of the internal member of the actuator may be accomplished in response to any known signal, such as electrical, hydraulic, or pneumatic. As with the manually operable handle, the movable internal member of the actuator is typically connected by a link member to the valve spool for movement therewith.
Regardless of whether the fluid control valve is operated by means of a manually operable handle or a remotely controllable actuator, some mechanical connection is necessary between the link member and the valve spool. This mechanical connection is sometimes difficult to achieve because the case of the fluid control valve is usually formed separately from the housing for the actuating mechanism, whether it be a manually operable handle or a remotely controllable actuator. Because of manufacturing tolerances, the axis of movement of the link member is rarely co-axial with the axis of movement of the valve spool connected thereto. Improper alignment of these axes can cause undesirable side loading or binding of the link member and the valve spool, resulting in premature wear and failure.
To address this, it is known to provide a mechanical connection between the link member and the valve spool which can accommodate a limited amount of misalignment between the respective axes of movement. However, known mechanical connections of this type have been somewhat complicated in structure and bulky in size. Furthermore, known mechanical connections do not always accommodate for misalignment in more than one plane. Thus, it would be desirable to provide an improved coupling structure for connecting a movable link member of a valve actuator to a movable valve spool in a fluid control valve which is simple, compact, and inexpensive in construction.